- A boat takes half time in moving a certain distance downstream than upstream. What is the ratio between rate of boat in still water and rate of current?
2:33:12:13:5NoneOption B

Solution:

Let the distance be xkm.

Then

2x/(u+v) = x/ (u-v)

2u – 2v = u+v

u:v=3:1.

- A boat covers a certain distance downstream in 2 hour, while it comes back in 2 1/2 hours. If the speed of the stream be 3 km/hr, what is the speed of the boat in still water?
20km/hr23km/hr27km/hr30km/hrNoneOption C

Solution:

Speed downstream = (u + 3) km/hr

Speed upstream = (u- 3) km/hr

(u+ 3) *2 = (u- 3) *5/2

4u+12=5u-15

u=27km/hr.

- If sum of upstream and downstream speed of a boat is 82 kmph, and the boat travels 105 km. upstream in 3 hr, Find the time taken by boat to cover 141 km downstream.
5hrs4hrs3hrs2hrsNoneOption C

Solution:

Speed of Upstream =u-v

Speed of Downstream = u+v

u-v+u+v=82

2u=82

u=41km/hr.

41 – v = 105/3 = 35

v = 6 km/hr

then,

u + v= 141/t

41 + 6 = 141/t

t = 141/47 = 3 hrs.

- A boatman goes 4 km against the current of the stream in 1 hour and goes 2 km along the current in 10 minutes. How long will it take to go 24 km in stationary water?
5hrs3hrs2hrs6hrsNoneOption B

Solution:

Upstream=4/1=4km/hr

Downstream=2*60/10=12km/hr

Speed in still water=(12+4)/2

=16/2=8km/hr.

For 24 km time=24/8

=3hrs.

- The speed of a boat in still water is 15 km/hr. It can go 30 km upstream and return downstream to the original point in 4 hrs 30 min. The speed of the stream is:
12km/hr8km/hr5km/hr10km/hrNoneOption C

Solution:

D=t [(u^{2}– v^{2}) /2u] 30 = 4 ½ *[(15^{2}– v^{2}) /2*15] 30=9/2 (225- v^{2})/30

200=225- v^{2}

v^{2}=25

v=5km/hr.

- A boat takes 12 hr to travel a distance upstream and takes 6 hr to travel the same distance downstream. If the speed of the boat in still water is 4 kmph, then what is the speed of the stream?
5km/hr1km/hr3km/hr2km/hrNoneOption B

Solution:

6(3+v) = 12(3-v)

18 +6v=36-12v

18v=18

v=1km/hr.

- A man can row 8 km/hr in still water. If it takes him thrice as long to row up, as to row down the river, then the rate of current in the stream would be
6.5km/hr4.5km/hr4km/hr5.5km/hrNoneOption C

Solution:

Ratio 3:1

u=8km/hr

(8-v)*3t = (8+v)*t

24-3v=8+v

4v=16

v=4km/hr.

- A man can row three-quarters of a kilometer against the stream in 45/4 minutes and return in 15/2 minutes. The speed of the stream
1km/hr3km/hr5km/hr4km/hrNoneOption A

Solution:

Upstream in 45/4min=3/4km

In 1 hr =3/4*4/45*60

=4km/hr.

Downstream in 15/2min=3/4km

In 1 hr=3/4*2/15*60

=6km/hr.

V=(6-4)/2

=2/2

=1km/hr.

- A boat running downstream covers 28 kms in 7 hours, while for covering the same distance upstream it takes 4 hours. What is the speed of the boat in still water and ?
4km/hr4.5km/hr5km/hr5.5km/hrNoneOption D

Solution:

Downstream=28/7=4km/hr

Upstream=28/4=7km/hr

Speed of the boat u=(4+7) /2

=11/2=5.5km/hr.

- A man can row 8 km/hr in still water. If the river is running at 3 km/hr, it takes 3 hours more in upstream than to go downstream for the same distance. How far is the place?
27.5km29km31.5km33kmNoneOption A

Solution:

D=3 (8^{2}-3^{2})/(2*3)

=(55*3)/6

=27.5km.